An expansion and upgrade to our Rigaku Macromolecular X-ray generator and detector system is requested. The expansion is a complete second X-ray port apparatus consisting of a Saturn 944 HG CCD detector VariMax HF Arc)Sec confocal optic, Oxford Cobra Cryostream cryo-cooling system, AFC11 Partial- 4 axis goniometer, video system for crystal centering and computer control. The instrument is located in the macromolecular X-ray core facility at the Yale University School of Medicine. These components will provide an experimental system with significantly increased X-ray fluence and detector sensitivity combined with dramatically faster data collection times. The improvements will facilitate currently unachievable experiments to be conducted in-house; thus, the proposed expansion is essential to completion of the NIH-funded research of the 8 major users, 1 minor user and 1 user funded by non-NIH sources. The aims of the research are to understand the molecular-level details of topics that include receptor tyrosine kinase dysregulation and inhibition in cancer, HIV reverse transcriptase function and novel therapeutic strategies for AIDS, integrin signaling cascades, regulation of serine/threonine kinases, regulation of non-receptor tyrosine kinases, regulation of calcium permeable TRP channels, GTPase signaling cascades, membrane proteases, chemokine signaling, membrane trafficking and neurotransmitter transporters. The institution (Yale University School of Medicine) has recently invested significantly in the structural biology core facility by renovations and purchase of crystallization robotics, a crystal plate imaging system, an HPLC for SEC with MALS, and an isothermal titration calorimetry system. The institution has offered significant additional supportif this proposal is successful.